Color filters used in display panels typically include a pattern comprising a plurality of color features. The color features may include patterns of red, green and/or blue color features, for example. Color filters may be made with color features of other colors. The color features may be arranged in any of various suitable configurations. Prior art “stripe” configurations have alternating columns of red, green and blue color features as shown in FIG. 1A.
FIG. 1A shows a portion of a prior art “stripe” configuration color filter 10 having a plurality of red, green and blue color features 12, 14 and 16 respectively formed in alternating columns across a receiver element 18. Color features 12, 14 and 16 are outlined by portions of a color filter matrix 20 (also referred to as matrix 20). The columns can be imaged in elongated stripes that are subdivided by matrix cells 31 (also referred to as cells 31) into individual color features 12, 14 and 16. TFT transistors on the associated LCD panel (not shown) may be masked by areas 22 of matrix 20.
Various imaging methods are known in the art and can be used to form various features on media. For example, laser-induced thermal transfer processes have been proposed for use in the fabrication of displays, and in particular color filters. In some manufacturing techniques, when laser-induced thermal transfer processes are used to produce a color filter, a color filter substrate also known as a receiver element is overlaid with a donor element that is then image-wise exposed to selectively transfer a colorant from the donor element to the receiver element. Preferred exposure methods use radiation beams such as laser beams to induce the transfer of the colorant to the receiver element. Diode lasers are particularly preferred for their low cost and small size.
Laser induced “thermal transfer” processes include: laser-induced “dye transfer” processes, laser-induced “melt transfer” processes, laser-induced “ablation transfer” processes, and laser-induced “mass transfer” processes. Colorants transferred during laser-induced thermal transfer processes include suitable dye-based or pigment-based compositions. Additional elements such as one or more binders may be transferred.
Some conventional laser imaging systems produce a limited number of radiation beams. Other conventional systems reduce the time required to complete images by producing many radiation beams with numerous individually-modulated imaging channels. Imaging heads with large numbers of such “channels” are available. For example, a SQUAREspot® model thermal imaging head manufactured by Kodak Graphic Communications Canada Company, British Columbia, Canada has several hundred independent channels. Each channel can have power in excess of 25 mW. An array of imaging channels can be controlled to write an image in a series of image swaths which are arranged to form a continuous image.
Radiation beams are scanned along a scan path to form various images. The visual quality of a formed image can be an important consideration in the selection of a particular imaging process. In applications such laser-induced thermal transfer of color filter features, the quality of the formed color filter is dependant on imaging features that have substantially the same visual characteristics. For example, one particular visual characteristic can include density (e.g. optical density or color density). Density variations among the imaged color features can lead to objectionable image artifacts. Image artifacts can include banding or color variations in imaged features.
The stripe configuration shown in FIG. 1A illustrates one example configuration of color filter features. Color filters may have other configurations. Mosaic configurations have the color features that alternate in both directions (e.g. along columns and rows) such that each color feature resembles an “island”. Delta configurations (not-shown) have groups of red, green and blue color features arranged in a triangular relationship to each other. Mosaic and delta configurations are examples of “island” configurations. FIG. 1B shows a portion of a prior art color filter 10 arranged in a mosaic configuration in which color features 12, 14 and 16 are arranged in columns and alternate both across and along the columns.
Other color filter configurations are also known in the art. Whereas the illustrated examples described above show patterns of rectangular shaped color filter elements, other patterns including other shaped features are also known.
FIG. 1C shows a portion of a prior art color filter 10 with a configuration of triangular shaped color features 12A, 14A and 16A. As illustrated in FIG. 1C, each of the respective color features are arranged along columns and are aligned with matrix 20.
FIG. 1D shows a portion of a prior art color filter 10 with a configuration of triangular shaped color features 12A, 14A and 16A. As illustrated in FIG. 1D, each of the respective color features alternate along the columns and rows of color filter 10. As shown in FIGS. 1C and 1D, color features 12A, 14A and 16A can have different orientations within a given row or column.
FIG. 1E shows a portion of a prior art color filter 10 that includes a configuration of chevron shaped color features 12B, 14B and 16B. As illustrated in FIG. 1E, each of the respective color features are arranged along columns and are aligned with matrix 20. Color features 12B, 14B and 16B are formed from stripes that bend from side to side and are outlined by portions of a color filter matrix 20.
FIG. 1F shows a portion of a prior art color filter 10 that includes a configuration of chevron shaped color features 12B, 14B and 16B. As illustrated in FIG. 1F, each of the respective color features alternate along the columns and rows of color filter 10.
The shape and configuration of a color filter feature can be selected to provide desired color filter attributes such as a better color mix or enhanced viewing angles. Features with edges that are skewed relative to a desired imaging scan direction can create additional challenges with respect to their fabrication.
In some applications, it is required that the features be formed in substantial alignment with a registration region provided on media. For example, in FIG. 1A the various color features 12, 14 and 16 are to be aligned with a pattern of matrix cells 34 that are provided by matrix 20. Color features 12, 14 and 16 can overlap matrix 20 to reduce backlight leakage effects. In some applications such as color filters, the visual quality of the final product can be dependant upon the accuracy with which a pattern of features (e.g. a pattern of color filter features) is aligned with a pattern of registration sub-regions (e.g. a color filter matrix). Misalignment can lead to the formation of undesired colorless voids or to the overlapping of adjacent features which can result in an undesired color characteristic.
While overlapping a matrix 20 can help to reduce the accuracy with which the color features must be registered with matrix 20 in color filter applications, there are typically limits to the extent that matrix 20 can be overlapped. Factors that can limit the degree of overlap (and final alignment) can include, but are not limited to: the particular configuration of the color filter, the width of the matrix lines, the roughness of the matrix lines, the overlap required for preventing backlight leakage, and post annealing shrinkage.
Factors associated with the particular method employed to form the features can limit the degree of overlap. For example, when laser imaging methods are employed, the accuracy with which the laser imager can scan the color filter will have a bearing on the final registration obtained. There is a desire in the display industry to employ color filter matrixes with thinner line widths. This desire can further complicate the alignment requirements.
The imaging resolution with which the features can be imaged also has a bearing on the final alignment. The imaging resolution is related to a size characteristic of an image pixel formed by a corresponding radiation beam during an imaging process. Higher resolutions can be used to form pixels with smaller dimensions. Smaller pixels may be combined to more precisely form imaged features. Higher resolutions however are not always possible however. For example, a radiation beam can be emitted to cause a radiation spot to be scanned across media to form a pixel thereupon. The size pixel in the scan direction is related to the size of the spot along the scan direction and the speed with which it is scanned along the scan direction. The size of the spot itself limits the imaging resolution that can be achieved along the scan direction. The size of the spot can be related to the switching frequency with which the radiation beam is emitted. Limits on the switching frequencies can therefore limit imaging resolution. Higher imaging resolution can also be limited by the imaged media itself. Exposure characteristics of the media can limit the size of the pixels that are formed. For example, in some thermal transfer processes, a radiation beam of suitable intensity is required to cause a region of image forming material to separate from a donor element and transfer to a receiver element. The transfer mechanism associated with the media can limit the use of high resolution pixels. However, forming features with relatively large pixels may limit the alignment that is achieved between the features and the registration regions they are to be aligned with. There remains a need for effective and practical imaging methods and systems that lead to the formation of high-quality images of patterns of features. Various portions of these features can have different orientations relative to a desired scanning direction. Various edges of these features can be skewed relative to a direction of a scan path.
There remains a need for effective and practical imaging methods and systems that can form features in substantial alignment with a pattern of registration sub-regions provided on media. Various edges of these features can be skewed relative to a direction of the scan path. The features can be part of a color display.
There remains a need for effective and practical imaging methods and systems that can form features with imaging resolutions that are relatively coarse in comparison with the size of the features themselves or with a desired tolerance required by a desired alignment of the features with a pattern of registration sub-regions provided on media. Various edges of these features can be skewed relative to a direction of the scan path. The features can be part of a color display.
There remains a need for effective and practical imaging methods and systems that can form color features in alignment with color filter matrix lines that have reduced line widths.